Currently, 24 states are considering legislation that would "mandate" vaccination against human papillomavirus (HPV), a sexually transmitted disease that causes cervical cancer, for girls entering middle school. These proposed mandates vary considerably between states with regard to financing and the criteria used to define mandate compliance. There is concern that some of the mandates under consideration may lead to policy- resistant behaviors whereby vaccine refusal was commonplace and socially acceptable. The broad objective of this application is to explore the potential impact of the different HPV vaccine mandates under consideration on attitudes about, and utilization of, three adolescent-targeted vaccines: HPV, Meningococcal conjugate vaccine (MCV4) and tetanus-diphtheria-acellular pertussis vaccine (Tdap). Our over-arching hypothesis is some HPV mandates under consideration could lead to policy resistant conditions that may not be intuitively predictable based on the assumptions we make about how the mandates affect individual-level behaviors. In our experiments, we will explore the role of social networks in propagating vaccine-related beliefs and behaviors. Specific Aim 1: To develop an agent-based model of adolescent vaccination that uses social networks to propagate attitudes about vaccines and vaccination behaviors. Specific Aim 2: To use the agent- based model to conduct a series of exploratory policy analyses examining how changes in assumptions about individual-level behaviors and attitudes following implementation of different HPV vaccine mandates alters population-level attitudes about, and utilization of, adolescent vaccines more broadly. Significance: These studies will provide insight into the role of social networks in promoting vaccine-related attitudes, which may identify targets for future interventions. In addition, these analyses will provide public health officials and policy makers with information crucial for understanding the factors and circumstances that could cause the HPV vaccine-related school mandates currently under consideration to succeed or fail. PUBLIC HEALTH RELEVANCE: Given the growing of vaccine refusal in the U.S., it is imperative to understand the circumstances under which school mandates for HPV vaccination could unintentionally worsen the public's view of vaccines. Because the different types of HPV vaccine-related school mandates currently under consideration cannot be tested empirically before their implementation, experimental modeling is the only mechanism available to discern the potential effects of these different policy options. The modeling approach we propose will provide policy makers and public health practitioners with highly valuable and timely information that could shape how policies regarding this vaccine are structured and implemented.